The purpose of this proposed research is to investigate the metabolism and role of prostaglandins, thomboxanes, prostacyclin, hydroxyeicosatetraenoic acids and leukotrienes in the retina. These potent chemical mediators of intercellular and intracellular signals are called eicosanoids. Specifically, we will test the hypothesis that eicosanoid synthesis and release are correlated with neurotransmission in the retina. Studies have been designed to explore retinal eicosanoid metabolism in relation to the release of chemical mediators and the postsynaptic action of neurotransmitters. Our preliminary studies have shown that the retina is able to synthesize a wide variety of eicosanoids and that a K+ evoked increase in the formation and release of 12-hydroxyeicosatetraenoic acid takes place. Hence, depletors of neurotransmitters, receptor agonists and antagonists, and light stimulation will be surveyed along with drugs that selectively inhibit steps of the metabolic pathways of eicosanoids. The following objectives will be addressed: a) a study of the activation, esterification, and release of arachidonic acid; how phosphoinositides and other phospholipids are involved as sources; and how eicosanoids are subsequently synthesized in the retina; b) the use of drugs as tools to understand the pathways of eicosanoid metabolism in the retina in vivo and in vitro, as well as the retinal subcellular sites involved; c) the examination of the activation mechanism of hydroxyeicosatetraenoic acid and subsequent incorporation into retinal lipids; d) the testing of the hypothesis that eicosanoid synthesis and release are correlated with neurotransmission in the retina by characterizing the K+ evoked stimulation of the synthesis and release of lipoxygenase reaction products and the effect of neurotransmitters on these processes; and e) the definition of the cellular localization of some eicosanoids and their participation in the scheme of information flow in the neural retina. To investigate retinal eicosanoid metabolism, we will inject precursors intravitreally into the rat eye, and follow the metabolic pathways and release upon stimulation by a combination of biochemical methods such as TLC, GLC, HPLC, radiochemical procedures, subcellular fractionation, and spectrophotometry. In addition, electrophysiological techniques and light microscopic and ultrastructural autoradiography will be used.